The present invention relates to visual image systems and, more particularly, relates to a visual image system in which the degree of three-dimensionality is controlled by estimating effects produced on the observer based on video signals.
Various proposals have been made with respect to visual image systems. For example, the following technique is disclosed in Japanese Patent Publication No.2594235 as that for converting two-dimensional visual image into three-dimensional visual image. In particular, a disclosure has been made with respect to a method for converting a two-dimensional visual image into a three-dimensional visual image in which the extent and direction of a horizontal motion in image is detected using a two-dimensional video signal by generating from the two-dimensional video signal a main video signal serving as a reference and a subordinate video signal delayed from the main video signal. The delay amount for generating subordinate video signal is then determined on the basis of an extent of motion and an image switching means for inputting the main or subordinate video signal is regulated depending on the direction of the motion, thereby providing an output with determining which one of the main or subordinate video signal is outputted as a left-eye video signal or a right-eye video signal.
Further, the following technique is disclosed in Japanese patent application laid open No.9-116928. In particular, a disclosure has been made with respect to technique for converting a two-dimensional visual image into a three-dimensional visual image in which a first phase-shifted visual image of which horizontal phase is gradually delayed by each one field along a vertical direction is produced based on a two-dimensional input image and a second phase-shifted visual image of which horizontal phase is gradually advanced by each one field along the vertical direction is produced based on the input image. One of the first phase-shifted and second phase-shifted images is used as a visual image for the left eye and the other is used for a visual image for the right eye.
It is generally said that the eyes are more likely to become fatigued when observing a stereoscopic image comparing to the case of observing an ordinary two-dimensional image. As a proposal considering this point, Japanese patent application laid open No.9-23451 discloses an apparatus for controlling stereoscopic condition as follows. In particular, a disclosure has been made with respect to a controlling apparatus in which: a sensor for detecting a temperature of skin at the forehead and a sensor for detecting a temperature of skin at the nose are set on glasses for viewing stereoscopic images so that a measure of excitation is provided from an excitation measure data converter based on their detected outputs; and a sensor for detecting blink is set on the glasses for viewing stereoscopic images so that a measure of fatigue is provided based on its detected output. A measure of enhancement on three-dimensionality is then outputted from a stereoscopic enhancement controlling circuit based on the degree of excitation and the degree of fatigue. The delay amount at a field memory of the stereoscopic television receiver for effecting 2D/3D conversion is controlled depending on this stereoscopic enhancement measure, thereby making it possible to control to a stereoscopic condition which is desirable according to the user's sensitivity.
In the case of controlling the degree of three-dimensionality of stereoscopic image based on the degree of excitation and degree of fatigue of the user as in the method of the above-mentioned disclosure, however, the biological measurements on the user vary greatly from one individual to another, making it difficult to determine from the biological measurements a limit value of fatigue measure which is suitable to all the observers. Furthermore, there is another problem that it is troublesome to individually obtain the measurements from each observer.